Omar Salma, 21, admitted bringing the weapon to the AFL clash between Collingwood and Carlton on April 3, which 82,000 fans attended.
He had assaulted a security guard, who evicted him from the ground two weeks earlier, when police arrived to restrain him.
During a search, officers uncovered a loaded .22 calibre revolver on Salma and a container of cartridge ammunition in his bag.
His co-offender Mohammad Noori also had a loaded firearm in his possession.
Salma told police he had the weapon to protect himself but magistrate Brett Sonnet on Friday described that reasoning as concerning.
"The fact a 21-year-old male believes it's necessary to carry a loaded firearm ... it's truly a worrying sign," Mr Sonnet said.
The magistrate noted Salma had carried out multiple violent attacks since 2022, including an incident at Crown Casino where he kicked and punched a man on an escalator.
But Mr Sonnet said the MCG incident was the most serious and alarming, given it was done in a public place with thousands of people present.
Salma was also prohibited from possessing a firearm at the time, the magistrate noted.
Mr Sonnet accepted Salma was still a young man and had developed a drug addiction following the death of a friend.
But a pre-sentence report showed Salma had a high risk of reoffending and he continued to minimise the seriousness of his conduct, the magistrate said.
Mr Sonnet concluded the offending was very serious and needed to be strongly condemned by the court.
Salma was jailed for 22 months but he will be eligible for parol in five months, having already served 155 days of his 10-month non-parole period.
His co-offender Noori was also jailed for 21 months but is appealing his sentence in the Victorian County Court.
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